An implant is used as an anchoring means for fixing a dental prosthesis when other fixing possibilities are lacking. Building up a dental prosthesis with this type of anchorage is initiated by an insertion by an operation of bone-fixtures in the jaw by making an incision in the gums and drilling bores in the jaw-bone, into which bores bone-fixtures in the form of root screws with a threaded, internal hole are screwed. A cover screw is placed in the internal hole of the root screw whereupon the gums are replaced. After a period of four to six months the implant has been osseointegrated with the jaw-bone and the cover screw is again uncovered and replaced by a spacing element, a pillar. The pillar is healed in under protection of a healing cap.
After completed healing the healing cap is removed and sockets are placed on the pillars and attached to said pillars with internal screws. After sealing of the open ends of the sockets, an impression of the jaw is made by depressing an impression tray filled with impression material on the jaw and the material is allowed to solidify. The upper ends of the sockets are uncovered from impression material and the internal screw is released. The solidified impression including the cast in sockets can now be removed and forwarded to a dental technician.
The dental technician builds up a positive working model of the jaw by, as a first step, attaching pillar dummies into the sockets which are cast in to the model and as a second step making an impression. The screws are released and the positive working model of the jaw in which pillar dummies are cast in can now be used to build up a dental bridge structure. On the pillar dummies, sockets are attached by screws and a continuous bridge structure, a wax model, is modelled of wax or plastic material. The wax model or the casting model must now be forwarded back to the dentist and tested on the patient to check that the matching to the anchoring elements is exact.
When the casting model is back with the dental technician, said model is used for preparation of a mold. This is prepared by pressing the model into a mold compound and burning the wax or plastic material out in a burning oven. A metal framework is cast in the completed mold to form a dental bridge into which the sockets are cast.
The method described above is complicated and suffers from certain disadvantages. Solely to build up the mold, two separate appointments with the dentist and in between work by the dental technician are needed. It has also been experienced that the completed casting model, when tested on the patient, often does not match exactly, which causes further treatments and subsequent adjustments. One disadvantage in this method is also the casting of the impression inside the mouth which is extremely unpleasant for the patient.